feat(output): implement configurable color and emoji output

Add new output formatting system with flags for color and emoji control:
- Introduce OutputConfig and Writer structs for flexible output handling
- Add --colors and --emoji/--no-emoji global flags
- Refactor commands to use new Writer for consistent formatting
- Separate error content from presentation for better flexibility

cmd/output.go

@@ -0,0 +1,230 @@
+package cmd
+
+import (
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/spf13/cobra"
+)
+
+// OutputConfig controls formatting behavior
+type OutputConfig struct {
+	Colors bool
+	Emoji  bool
+}
+
+// Writer provides formatted output with configurable styling
+type Writer struct {
+	out    io.Writer
+	config OutputConfig
+	err    error // first error encountered
+}
+
+// NewWriter creates a new Writer with the given configuration
+func NewWriter(out io.Writer, config OutputConfig) *Writer {
+	return &Writer{
+		out:    out,
+		config: config,
+	}
+}
+
+// Message represents a structured message with optional formatting
+type Message struct {
+	Text  string
+	Color string
+	Emoji string
+	Bold  bool
+}
+
+// Write outputs a message according to the writer's configuration
+func (w *Writer) Write(msg Message) *Writer {
+	if w.err != nil {
+		return w
+	}
+
+	var output string
+
+	// Add emoji if enabled
+	if w.config.Emoji && msg.Emoji != "" {
+		output = msg.Emoji + " "
+	}
+
+	// Add color/bold if enabled
+	if w.config.Colors {
+		if msg.Bold {
+			output += "\033[1m"
+		}
+		if msg.Color != "" {
+			output += msg.Color
+		}
+	}
+
+	output += msg.Text
+
+	// Close formatting if enabled
+	if w.config.Colors && (msg.Bold || msg.Color != "") {
+		output += "\033[0m"
+	}
+
+	_, w.err = fmt.Fprint(w.out, output)
+	return w
+}
+
+// Printf is like Write but with format string
+func (w *Writer) Printf(msg Message, args ...any) *Writer {
+	newMsg := msg
+	newMsg.Text = fmt.Sprintf(msg.Text, args...)
+	return w.Write(newMsg)
+}
+
+// Writeln writes a message followed by a newline
+func (w *Writer) Writeln(msg Message) *Writer {
+	return w.Write(msg).WriteString("\n")
+}
+
+// WriteString outputs plain text (no formatting)
+func (w *Writer) WriteString(text string) *Writer {
+	if w.err != nil {
+		return w
+	}
+	_, w.err = fmt.Fprint(w.out, text)
+	return w
+}
+
+// WritelnString outputs plain text followed by a newline
+func (w *Writer) WritelnString(text string) *Writer {
+	if w.err != nil {
+		return w
+	}
+
+	_, w.err = fmt.Fprintln(w.out, text)
+	return w
+}
+
+// ANSI color codes
+const (
+	ColorRed          = "\033[31m"
+	ColorYellow       = "\033[33m"
+	ColorCyan         = "\033[36m"
+	ColorGray         = "\033[90m"
+	ColorBrightGreen  = "\033[1;32m"
+	ColorBrightYellow = "\033[1;33m"
+	ColorBrightRed    = "\033[1;31m"
+)
+
+// Predefined message constructors for common patterns
+
+func Success(text string) Message {
+	return Message{Text: text, Color: ColorBrightGreen, Emoji: "✅", Bold: true}
+}
+
+func Error(text string) Message {
+	return Message{Text: text, Emoji: "❌"}
+}
+
+func Warning(text string) Message {
+	return Message{Text: text, Color: ColorBrightYellow, Emoji: "⚠️", Bold: true}
+}
+
+func Info(text string) Message {
+	return Message{Text: text, Color: ColorYellow, Emoji: "💡"}
+}
+
+func Target(text string) Message {
+	return Message{Text: text, Emoji: "🎯", Bold: true}
+}
+
+func Rocket(text string) Message {
+	return Message{Text: text, Emoji: "🚀", Bold: true}
+}
+
+func Sparkles(text string) Message {
+	return Message{Text: text, Emoji: "✨", Bold: true}
+}
+
+func Link(text string) Message {
+	return Message{Text: text, Color: ColorCyan, Emoji: "🔗"}
+}
+
+func Plain(text string) Message {
+	return Message{Text: text}
+}
+
+func Bold(text string) Message {
+	return Message{Text: text, Bold: true}
+}
+
+func Colored(text, color string) Message {
+	return Message{Text: text, Color: color}
+}
+
+// Global output configuration
+var (
+	globalConfig = OutputConfig{
+		Colors: true, // auto-detect on first use
+		Emoji:  true,
+	}
+	autoDetected bool
+)
+
+// SetGlobalConfig updates the global output configuration
+func SetGlobalConfig(colors string, emoji bool) error {
+	switch colors {
+	case "auto":
+		globalConfig.Colors = isTerminal()
+	case "always":
+		globalConfig.Colors = true
+	case "never":
+		globalConfig.Colors = false
+	default:
+		return fmt.Errorf("invalid color mode: %s (valid: auto, always, never)", colors)
+	}
+
+	// Check NO_COLOR environment variable (explicit flag takes precedence)
+	if os.Getenv("NO_COLOR") != "" && colors == "auto" {
+		globalConfig.Colors = false
+	}
+
+	globalConfig.Emoji = emoji
+	autoDetected = true
+	return nil
+}
+
+// isTerminal checks if stdout is a terminal
+func isTerminal() bool {
+	fileInfo, err := os.Stdout.Stat()
+	if err != nil {
+		return false
+	}
+	return (fileInfo.Mode() & os.ModeCharDevice) != 0
+}
+
+// autoDetectConfig performs one-time auto-detection if not explicitly configured
+func autoDetectConfig() {
+	if !autoDetected {
+		if os.Getenv("NO_COLOR") != "" {
+			globalConfig.Colors = false
+		} else {
+			globalConfig.Colors = isTerminal()
+		}
+		autoDetected = true
+	}
+}
+
+// GetWriter returns a writer for the given cobra command
+func GetWriter(cmd *cobra.Command) *Writer {
+	autoDetectConfig()
+	return NewWriter(cmd.OutOrStdout(), globalConfig)
+}
+
+// GetErrorWriter returns a writer for stderr
+func GetErrorWriter() *Writer {
+	autoDetectConfig()
+	return NewWriter(os.Stderr, globalConfig)
+}
+
+// Err returns the first error encountered during writing
+func (w *Writer) Err() error {
+	return w.err
+}